1. Field of the Invention
The present invention relates generally to a heat exchanger. More specifically, the present invention relates to a heat transfer tube for a heat exchanger.
2. Related Technology
Heat exchanger assemblies, such as radiators, heater cores, and condensers, for automotive vehicle powertrain cooling and air conditioning systems typically include a pair of headers and a core having a plurality of tubes disposed horizontally between the two headers. Within the headers, partitions divide the interior space of the headers into multiple, fluidly separate spaces. As a result, refrigerant passing through the heat exchanger is caused to flow generally horizontally along the length of the tubes, in a serpentine fashion, making more than one pass between the headers. A plurality of thin heat exchange fins extend generally vertically from the top and bottom surfaces of the tubes to increase the surface area of heat exchanging components.
During operation of the heat exchanger, air flows across the exterior of the tubes and between the fins in a direction generally perpendicular to the length of the tubes. In order to maximize the heat exchange between the fins and the air flowing therethrough, the fins and the tubes have an increased width in the direction parallel to the airflow. Additionally, to decrease the wind resistance on the airflow, the tubes have a decreased thickness in the direction perpendicular to the airflow. Thus, the tubes preferably have a generally oblong shape with relatively small end faces and relatively large top and bottom faces.
The non-circular cross-section of the tubes, however, may cause non-constant stress along the perimeter of the tubes. More specifically, the oblong configuration causes increased stress in the curved areas between the end faces and the top and bottom faces. Therefore, the tubes may be subject to premature part failure along these increased stress areas.
Furthermore, the walls of the tubes have a minimum thickness to maximize heat exchange between the refrigerant and the airflow. Thus, it may be undesirable to increase the thickness of the tube walls to compensate for potential increased stress areas.
Therefore, it is desirable to provide heat exchange tubes having enhanced strength and a method of manufacturing such tubes.